Microalgae cultivation in high rate algal ponds using slaughterhouse wastewater for biofuel applications

The performance of two 75-L high rate algal ponds (HRAPs) treating slaughterhouse wastewater was evaluated for 115 days with the aim of growing microalgae to produce biofuels (biodiesel, methane). One HRAP was placed indoors under controlled conditions of temperature (25 ± 2 °C) and light supply, while the other was placed in a greenhouse under 20 ± 6 °C and 9-fold higher light supply. The hydraulic retention time (HRT) was decreased from 15 to 10 days. High removal efficiencies were achieved in HRAP placed indoors (92% and 71%) and placed in the greenhouse (86% and 91%) for total chemical oxygen demand and soluble phosphorous, respectively. The maximum biomass production obtained was 12.7 g volatile suspended solids (VSS)/m2 day. High quality fatty acids (FFA) were extracted by supercritical carbon dioxide, obtaining 142 mg FFA/g biomass. The highest CH4 productions were obtained from lipid exhausted biomass corresponding to greenhouse HRAP at a HRT of 10 days (195 mL CH4/g VSSadded).